In the art, there are numerous substances which are sensitive to light energy. The substances of interest generally fall into two classes. The first class comprises substances which undergo polymerization in response to applied light energy. The second class comprise substances which produce a "singlet oxidation molecule" in response to applied light energy. The second class of substances can be found in "photodynamic therapy" or "phototherapy" applications, while the first class of photo-sensitive substances are typically found in UV polymerization and photochemical curing of adhesives.
It is known that the time it takes to cure a photosensitive adhesive is influenced by two principal factors. The first factor encompasses the type of adhesive and amount which is required for the application. Once determined for the particular application, this factor remains fixed for the application. The second factor affecting the cure time involves the amount of light energy being delivered to the cure the adhesive. It is also known that the intensity level produced by the light source will decrease over the life of the source. As the intensity level degrades so will the amount of light energy being delivered to cure the adhesive and therefore a longer exposure time is needed to properly cure the adhesive.
While known photochemical curing systems provide the capability to adjust the exposure time, they do not monitor the ongoing degradation of the intensity level produced by the light source. Thus, the performance of such a prior art system will steadily degrade over time unless the intensity level is manually measured and the exposure time adjusted accordingly.
Furthermore, in some applications, it may be desirable to increase the intensity level instead of the exposure time in order to provide an light energy output which is optimum for the curing application. Moreover, the light energy output level should be maintained at a consistent level over the operable life of the light source.